# Sodium chloride is NaCl, and sodium sulfide is Na_2S. Why are there more sodium ions in the sulfide compound?

Sodium chloride is composed of $N {a}^{+}$ ions and $C {l}^{-}$ ions. Now of course salt is neutral; and to ensure this sodium ion and chloride ions combine 1:1.
On the other hand, sulfur commonly forms an ${S}^{2 -}$ ion. (Sulfur is a $\text{Group VI}$ atom, and its chemistry is similar to oxygen, which certainly forms the ${O}^{2 -} \text{, oxide}$ ion.) Since sodium sulfide is a neutral salt, each sulfide ion requires $2 \times N {a}^{+}$ ions. Capisce?
Why are there $3$ sodium atoms in $N {a}_{3} P$?